Song structure (popular music)
From The Art and Popular Culture Encyclopedia
The structures or musical forms of songs in popular music are typically sectional, repeating forms, such as strophic form. Other common forms include thirty-two-bar form, verse-chorus form, and the twelve bar blues. Popular music songs are rarely composed using different music for each stanza of the lyrics (songs composed in this fashion are said to be "through-composed").
The verse and chorus are considered the primary elements. Each verse usually has the same melody (possibly with some slight modifications), but the lyrics change for most verses. The chorus (or "refrain") usually has a melodic phrase and a key lyrical line which is repeated. Pop songs may have an introduction and coda ("tag"), but these elements are that part essential to the identity of most songs. Pop songs that use verses and choruses often have a bridge, which, as its name suggests, is a section which connects the verse and chorus at one or more points in the song.
The verse and chorus are usually repeated throughout a song though the bridge, intro, and coda (also called an "outro") are usually only used once. Some pop songs may have a solo section, particularly in rock or blues influenced pop. During the solo section one or more instruments play a melodic line which may be the melody used by the singer, or, in blues or jazz influenced pop, the solo may be improvised based on the chord progression.